Anionic microgels for colorful smart materials

Microgels are a class of soft materials that have been used in almost all fields, including drug
delivery, food science, biocatalyis, and formulation. The wide range of possible application
relies on their hybrid nature, bridging linear macromolecules, hard colloids, and surfactants.
One of the most well-studied characteristics of microgels is their rapid response to external
stimuli. Depending on their chemical design, microgels can be responsive to temperature,
pH, ionic strength, light, electrochemical potential, or molecular cues. Microgels responsive
to multiple stimuli exist, e.g. thermoresponsive anionic microgels decorated with COOH
which are responsive to changes in both temperature and pH. While the phase behaviour of
such microgels in response to these stimuli has been well characterized, an additional mode
of responsiveness inherent to the same chemical formulations has barely been investigated:
Their response to the presence of divalent cations that can enter metal-ligand interactions
with COOH groups. Moreover, previous studies regarding these fascinating and versatile
microgels have been limited to studying their responsiveness, but have yet to explore their
use as soft composites for macroscopic applications.
This thesis presents some applications that thermoresponsive anionic microgels can
offer beyond merely swelling/deswelling in response to changes in temperature or pH. The
microgels presented were chemically tailored to fit the application presented for each chapter.
Briefly, this thesis presents in Chapters 2 and 3, poly(vinylcaprolactam-co-itaconic acid)
P(VCL-co-IA) microgels and their interactions with biologically-relevant divalent cations.
Detailing the investigation of swelling behaviour, uptake, release, and ion selectivity to
produce biocompatible ion delivery systems for biomedical and synthetic biology applications.
Chapter 4 describes the use of poly(N-isopropylacrylamide-co-methacrylic acid) (P(NIPAm-
co-MAAc)) microgels as building blocks for granular double-network hydrogels, which are
mechano- and thermochromic. This simple, yet effective approach to make structurally-
colored gels inspired attempts to shape the same gels via additive manufacturing, outlined in
Chapter 5. Microgels can be used not only as building blocks for large composite materials but
also as models for soft and compartmentalized reactions in synthetic cells. Chapter 6 presents
their encapsulation in synthetic, block copolymer-based membrane compartments, and describes their behaviour in crowded environments, with potential applications in synthetic
biology.